The present invention relates to a sensor for the measurement of accelerations having a substantially one-dimensionally deflectable mass part which is spring mounted in a housing and a distance measurement device with transmitter and receiver which operates without contact.
Such sensors are employed in motor vehicles for producing a signal for triggering an air bag, for activating a belt-tightening system, or for detecting acceleration values for control of a running gear. They must be operable without limitation over a wide range of temperatures and must not lose their reliability in operation for a long period of time. Furthermore, they should be as simple and inexpensive as possible.
A sensor for the above-mentioned field of use is known from German OS 35 38 766. The sensor element is developed in the form of a flexural oscillator with or without additional mass coupling, the acceleration-induced mechanical deformation of which is detected by a distance measurement method which operates without contact and is delivered as electrical signal. In this connection, two sensors are arranged in such a manner that the sum of their output signals corresponds to twice the linear acceleration and their difference is a measure of a rotary acceleration.
This known acceleration sensor has the disadvantage that a non-linear signal is obtained with which it is not possible to determine whether, in the case of a difference in signals, a rotational acceleration is present, or whether an age-induced change in the sensor data or in mechanical construction has occurred. Furthermore, two highly accurate sensors are required for detection of a distance requiring sensors to detect an entire range of deflection of a flexural oscillator. The setting of the zero points for both sensors is very difficult.